Add Galaxy repository API and clients

docs/gateway-dashboard-design.md

@@ -48,10 +48,20 @@ Endpoint layout:
 /dashboard/sessions/{sessionId}
 /dashboard/workers
 /dashboard/events
+/dashboard/galaxy
 /dashboard/settings
 /dashboard/_blazor
 ```
 
+The `/dashboard/galaxy` page surfaces the Galaxy Repository browse summary
+(deployed object hierarchy size, last deploy timestamp, attribute totals,
+template usage, and connectivity sync info). The summary is fed by
+`GalaxySummaryCache`, which is refreshed off the request path by
+`GalaxySummaryRefreshService` on the
+`MxGateway:Galaxy:DashboardRefreshIntervalSeconds` cadence so the dashboard
+never blocks on SQL. See [Galaxy Repository Browse](./GalaxyRepository.md) for
+the underlying gRPC service.
+
 The app should redirect `/` to `/dashboard` only if the deployment wants the
 dashboard as the default web page. Otherwise leave gRPC/API hosting unaffected.